同型半胱氨酸影响肝蛋白酪氨酸磷酸酶 1B 的作用及其机制。

Role and mechanism of homocysteine in affecting hepatic protein-tyrosine phosphatase 1B.

机构信息

Medical School, University of Chinese Academy of Sciences, the Campus of Yanqi, Huai Rou, 101407 Beijing, China.

出版信息

Biochim Biophys Acta Gen Subj. 2019 May;1863(5):941-949. doi: 10.1016/j.bbagen.2019.03.007. Epub 2019 Mar 7.

DOI:10.1016/j.bbagen.2019.03.007

PMID:30853337

Abstract

BACKGROUND

Elevated homocysteine is epidemiologically related to insulin resistance. Protein-tyrosine phosphatase 1B (PTP1B) is a negative regulator of insulin signaling. However, the effect of homocysteine on PTP1B remains unclear.

METHODS

S-homocysteinylated PTP1B was identified by LC-ESI-MS/MS. The ability of thioredoxin system to recover active PTP1B from S-homocysteinylated PTP1B was confirmed by RNA interference. To address the mechanism for homocysteine to affect PTP1B activity, we performed 5-IAF insertion, activity assays, Western blotting, co-immunoprecipitation and glucose uptake experiments.

RESULTS

The thiol-containing form of homocysteine (HcySH) suppressed phosphorylation of insulin receptor-β subunit, but enhanced PTP1B activity. This phenomenon was partially related to the fact that HcySH promoted PTP1B expression. Although the disulfide-bonded form of homocysteine (HSSH) modified PTP1B to form an inactive S-homocysteinylated PTP1B, HcySH-induced increase in the activities of cellular thioredoxin and thioredoxin reductase, components of thioredoxin system, could recover active PTP1B from S-homocysteinylated PTP1B. Thioredoxin system transferred electrons from NADPH to S-homocysteinylated PTP1B, regenerating active PTP1B in vitro and in hepatocytes. The actions of HcySH were also related with decrease in hepatic glucose uptake.

CONCLUSIONS

The effect of HcySH/HSSH on PTP1B activity depends, at least partially, on the ratio of active PTP1B and S-homocysteinylated PTP1B. High HcySH-induced an increase in thioredoxin system activity is beneficial to de-S-homocysteinylation and is good for PTP1B activity.

GENERAL SIGNIFICANCE

Our data provide a novel insight into post-translational regulation of PTP1B, and expand the biological functions of thioredoxin system.

摘要

背景

同型半胱氨酸水平升高与胰岛素抵抗在流行病学上有关。蛋白酪氨酸磷酸酶 1B（PTP1B）是胰岛素信号的负调节因子。然而，同型半胱氨酸对 PTP1B 的影响尚不清楚。

方法

通过 LC-ESI-MS/MS 鉴定 S-同型半胱氨酸化的 PTP1B。通过 RNA 干扰证实了硫氧还蛋白系统从 S-同型半胱氨酸化的 PTP1B 中恢复活性 PTP1B 的能力。为了探讨同型半胱氨酸影响 PTP1B 活性的机制，我们进行了 5-IAF 插入、活性测定、Western blot、共免疫沉淀和葡萄糖摄取实验。

结果

含巯基的同型半胱氨酸（HcySH）抑制胰岛素受体-β亚基的磷酸化，但增强 PTP1B 活性。这种现象部分与 HcySH 促进 PTP1B 表达有关。尽管同型半胱氨酸的二硫键形式（HSSH）修饰 PTP1B 形成无活性的 S-同型半胱氨酸化 PTP1B，但细胞硫氧还蛋白和硫氧还蛋白还原酶（硫氧还蛋白系统的组成部分）活性的增加会从 S-同型半胱氨酸化 PTP1B 中恢复活性 PTP1B。硫氧还蛋白系统将电子从 NADPH 转移到 S-同型半胱氨酸化 PTP1B，在体外和肝细胞中重新生成活性 PTP1B。HcySH 的作用也与肝葡萄糖摄取减少有关。